Both components of that primary endpoint were likewise similar between groups, the researchers reported here at the European Society of Cardiology meeting and simultaneously online in the New England Journal of Medicine.

The trial is the first to directly address whether the regurgitation is a consequence, cause, or just marker of the disease, Obadia noted, pointing to the class 2b recommendation in guidelines for percutaneous repair.

"Before this study we had absolutely no answer, and we used the clip very liberally. That was probably one extreme," Obadia said at a press conference for the late-breaking clinical trial session.

Now the findings say that "most probably the main cause of the disease is the underlying cardiomyopathy and the regurgitation is probably just a signal or marker of the disease but not the real cause," he said. "To treat the valve is probably to treat the consequence and not the cause."

But he recommended against going to the other extreme and stopping use entirely based on a single randomized trial. "What I would suggest is we should be more restrictive in the indication. But since I cannot exclude that in some subgroup of patients the clip would be useful, I think it is important to keep the door open. There are probably some patients where they are very high risk that the clip could be useful."

The device had worked as expected, with a 96% successful implantation rate and 95% improving at least one grade in mitral regurgitation, 75% to a trace or less of regurgitation.

And it was "very safe," Obadia said. While stroke, need for dialysis, and severe hemorrhage were more common with the intervention, Obadia pointed to the 3.5% rate of complications requiring surgery or transfusion.

However, high quality medical therapy also improves symptoms, Obadia countered. "We cannot rely on the registries."

Answers are more likely to come from the COAPT trial, due to be reported at the Transcatheter Cardiovascular Therapeutics meeting next month, he said. It studied largely the same population randomized to MitraClip or optimal medical therapy, but nuances in how the procedure is done could make a difference, commented Richard Becker, MD, of the University of Cincinnati, Ohio.

MITRA-FR may suggest that COAPT too will be negative, speculated Anthony DeMaria, MD, of the University of California San Diego.

“If I were a betting man, I would have bet against both of these, because nothing in functional mitral regurgitation has really been successful,” he told MedPage Today. “But cross your fingers and hope against hope it’s positive, because there are so many of these patients and there’s not a lot you can do for them short of transplant and LVAD [left ventricular assist device] and things like that as they deteriorate.”

MITRA-FR included 307 patients with severe secondary mitral regurgitation with a regurgitant volume of greater than 30 ml per beat or an effective regurgitant orifice area of greater than 20 mm2 on echocardiography, left ventricular ejection fraction between 15% and 40%, and New York Heart Association (NYHA) functional class II, III, or IV symptomatic chronic heart disease. Candidates for mitral-valve surgery were excluded.

Participants were randomized to open-label treatment with MitraClip or medical therapy alone at 37 centers in France with some MitraClip experience.

Findings were similar across subgroups by ejection fraction, regurgitation orifice size, and other measures, although Obadia urged caution against taking the subgroup analyses as gospel.

Study discussant Stephan Windecker, MD, of the Swiss Cardiovascular Center Bern, pushed back on the findings, calling the trial underpowered to find small differences and with a population of the sickest mitral valve patients studied so far. He highlighted the convincing efficacy in reducing mitral regurgitation, its "exceedingly safe" use, and suggested that the heart team still consider MitraClip use as palliative treatment for selected patients who remain highly symptomatic despite medical therapy.

In such highly-selected patients, there is an immediate impact on symptoms, noted Kurt Huber, MD, of the Medical University of Vienna. "I think in the future these patients will still get these devices, but we shouldn't do it in every patient because it's very important to do optimal medical therapy."

“From an administrator’s perspective where we have to make decisions about what we offer in our institution, how we talk to our public, secondary mitral insufficiency is one of those where we’ve always been cautious, but it’s being done far and wide,” Becker noted.

“This would cause many to pause, think carefully about what’s being offered,” he added. “If we don’t reduce rehospitalization for heart failure and you don’t change cardiovascular mortality, the question is, what are you offering?”

Less severe cases might be important to study though, as intervening at an earlier stage of pathology could potentially have a bigger impact, Obadia noted.

The trial was supported by the French Ministry of Health and Research National Program and Abbott Vascular.

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